1. Technical Field
The present invention relates to a method of controlling an illumination apparatus, and in particular, to a method of controlling an illumination apparatus having organic electroluminescence elements.
2. Background Art
An organic electroluminescence element (hereinafter, referred to as an organic EL element) has a structure in which an organic EL layer including a light-emitting layer and electrodes including an anode and a cathode arranged to face each other with the organic EL layer interposed therebetween are laminated on a substrate. At the time of the turn-on of the organic EL element configured as above, defects, such as short-circuit between the electrodes, may occur due to mixing of foreign substances in the organic layer during manufacturing or formation irregularity of the organic layer.
In order to cope with such defects, when defects, such as short-circuit, are found in product checking during manufacturing, defective elements are excluded or restored. However, since the organic EL element is formed of an organic material, alteration, such as thermal decomposition, may occur or molecular diffusion of organic molecules, such as electrophoresis, due to an electric field applied at the time of the turn-on may occur. For this reason, after shipment, defects, such as short-circuit between the electrodes of an organic EL element being used, may occur.
In an illumination apparatus having organic EL elements, if a short-circuit malfunction occurs in an organic EL element, since a short-circuited area is not turned on and a large current flows in the short-circuited area, the emission state of a different organic EL element to which power is supplied from the same power feed unit is darkened or is not turned on. As a result, irregularity in the emission state of the illumination apparatus, such as luminance, occurs over a wide range, and a non-conduction malfunction, such as disconnection of an organic EL element or wiring, occurs due to a rise in temperature of a specific element, causing degradation in quality.
In particular, when a plurality of organic EL elements having different emission colors are arranged to form a light-emitting surface of an illumination apparatus, if an organic EL element having a specific emission color is not turned on, an illumination color changes or color irregularity in an emission color occurs, and a non-conduction malfunction occurs due to a rise in temperature of a specific element, causing degradation in quality. Furthermore, the number of not-turned-on elements increases, and the appearance of the illumination apparatus is deteriorated.
As a method of restoring a short-circuit malfunction, a method in which an overcurrent flows in the short-circuited area with the application of a reverse voltage pulse to the short-circuited area to generate Joule heat, and the short-circuited area is disconnected using heat and restored (JP-A-11-162637), and a method in which a reverse bias voltage is applied to the short-circuited area to disconnect and restore the short-circuited area (JP-A-2007-207703) are known. A method in which a device for diagnosis is used to diagnose a malfunction state of an organic EL element (JP-T-2010-524151) is also known.